Conventional copying machines serving as an image forming apparatus are generally provided with a plurality of paper feed cassettes, i.e., a cassette for each paper size. It is preferable in view of the feeding speed to feed copy paper laterally oriented with respect to a feed direction (this way of paper feeding is hereinafter referred to as "lateral feed") rather than to feed copy paper longitudinally oriented with respect to the feed direction (this way of paper feeding is hereinafter referred to as "longitudinal feed"). In fact, not only small size copy papers but large size copy papers such as B4-size copy paper and A3-size copy paper are laterally fed in some copying machines.
However, in order to accept large size copy paper laterally fed, the sizes of the photosensitive drum, delivery roller and paper feed path within the main body of the copying machine have to be increased, resulting in a bulky and costly copying machine. Therefore, copying machines are generally arranged such that large size papers such as B4-size paper and A3-size paper are longitudinally fed while small size papers such as A4-size paper are laterally fed.
Such an arrangement is not suitable for a copying machine having a variable magnification function for image enlargement and reduction, because a B5R cassette for feeding B5-size paper longitudinally oriented and a A4R cassette for feeding A4-size paper longitudinally oriented are needed in order to perform reduction copying operation while a B5 cassette and a A4 cassette for lateral feed are needed in consideration of the feeding speed. There arise still some problems in providing a variety of paper cassettes in a copying machine: that is, the size of the copying machine have to be increased; or a plurality of paper cassettes have to be changed according to purposes when copying. As a result, the apparatus becomes bulky and costly; the operation will otherwise be more troublesome.
A number of approaches to solve the foregoing problems have been provided. One solution is disclosed in Japanese Patent Publication (laid-open) No. 59245/1981 (Tokukaisho 56-59245) and Japanese Patent Publication (laid-open) No. 123859/1984 (Tokukaisho 59-123859): in those inventions, a B5 cassette is also used as a B5R cassette and a A4 cassette as a A4R cassette, that is, one cassette is used both for lateral feed and longitudinal feed by changing the orientation of copy paper stored in the cassette.
In Japanese Patent Publication 59245/1981, whenever a magnification mode is switched from real size copying to reduction/enlargement copying or vice versa, the rotating section of a specified rotatble cassette, the rotating section on which copy paper is stacked, is turned to a longitudinal feed position or lateral feed position.
In the case the above arrangement (i.e., the rotating section of a specified rotatable cassette is rotated whenever a magnification mode is changed) is applied to a copying machine having an automatic paper selection function in which a cassette storing paper to be used is automatically selected according to a document size/orientation and a specified magnification rate, if an error occurs in detection of the document size/orientation, the rotating section of a specified rotatable cassette is rotated every time when the data of the document size/orientation are changed. In such a case, the rotating section is forced into undesirable rotations, and consequently, the office environment is considerably disturbed by noise caused by the rotations of the rotating section.